.\" Copyright (c) 2008 George V. Neville-Neil
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.Dd July 9, 2008
.Dt MCGRAB 1
.Os
.Sh NAME
.Nm mcgrab
.Nd "multicast filter overload test"
.Sh SYNOPSIS
.Nm
.Op Fl i Ar interface
.Op Fl g Ar group
.Op Fl n Ar number
.Sh DESCRIPTION
The
.Nm
command implements a multicast test which grabs and holds
N multicast addresses.
The purpose of the test is to see what
happens when a network interface is no longer able to filter
multicasts in hardware and has to switch to promiscuous or
multicast promiscuous mode.
A successful test does not have any
result, but an unsuccessful test will have deleterious side effects.
Packet size in bytes.
The options are as follows:
.Bl -tag -width ".Fl i Ar interface"
.It Fl i Ar interface
Network interface, which can be found with
.Xr ifconfig 8 .
.It Fl g Ar group
Multicast group.
.It Fl n Ar number
Number of groups to join.
.El
.Sh EXAMPLES
The following is an example of a typical usage
of the
.Nm
command:
.Pp
.Dl "mcgrab -i em0 -g 239.255.255.1 -n 1024"
.Sh SEE ALSO
.Xr mctest 1 ,
.Xr netstat 1 ,
.Xr nanosleep 2 ,
.Xr ifconfig 8
.Sh HISTORY
The
.Nm
program first appeared in
.Fx 7.0 .
.Sh AUTHORS
This
manual page was written by
.An George V. Neville-Neil Aq Mt gnn@FreeBSD.org .
.Sh BUGS
Should be reported to the author or to
.Aq Mt net@FreeBSD.org .
